THE ROLE OF 18F-FDG PET/CT IN MONITORING RECURRENCE OF COLORECTAL CANCER IN PATIENTS WITH RISING CEA LEVELS

Abstract

Colerectal cancer is considered the third leading cause of cancer worldwide with recurrence taking place in about a third of the patients within 2 years post surgery. Early detection and surgical resection of recurrent colorectal cancer significantly improves survival of the patients and has become more important over the last decade as management options for local disease improved greatly. Assessment of theraputic response topre-operative chemotherapy is becoming fundamental practice in order to decide the best chemotherapy protocol orwhen to go for surgical treatment. Conventional CT and MRI only offer anatomical and morphological mapping of of the tumors with no information about the metabolic activity. Lately, PET imaging for tumor staging and monitoring therapy response has been introduced. PET imaging only provides physiologic information on glucose uptake and metabolism, the main downside to PET imging in tumors is the lack of accurate anatomical landmarks which makes localizing the lesion hard.

Combined PET/CT provides both the anatomic and metabolic imaging at the same time. It also makes separating normal physiological uptake from pathological uptake more feasable. It has higher sensitivety and specificity and reduces false-positive and false-negative imaging studies. PET/CT is currently indespensible for colorectal cancer patients in monitoring recurrence where it is highly beneficial in detecting recurrence as early as possible thereby, significantly improving survival chances.Also, it is used in assessment of response to therapy to decide for the best treatment option for the patient as it can differentiate between residual metabolically active tumor and areas of nectosis and fibrosis.